21253112100 has 180 divisors, whose sum is σ = 75157616688. Its totient is φ = 5152248000.

The previous prime is 21253112099. The next prime is 21253112113. The reversal of 21253112100 is 121135212.

21253112100 is a `hidden beast` number, since 2 + 12 + 531 + 121 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (180).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 30166 + ... + 208365.

Almost surely, 2^21253112100 is an apocalyptic number.

21253112100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21253112100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37578808344).

21253112100 is an abundant number, since it is smaller than the sum of its proper divisors (53904504588).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21253112100 is a wasteful number, since it uses less digits than its factorization.

21253112100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238568 (or 238552 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

Adding to 21253112100 its reverse (121135212), we get a palindrome (21374247312).

The spelling of 21253112100 in words is "twenty-one billion, two hundred fifty-three million, one hundred twelve thousand, one hundred".